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971.
972.
Aijuan Wang Yunshan Ge Jianwei Tan Mingliang Fu Asad Naeem Shah Yan Ding Hong Zhao Bin Liang 《环境科学学报(英文版)》2011,23(3):419-426
On-road emission and fuel consumption (FC) levels for Euro III and IV buses fueled on diesel and compressed natural gas (CNG)
were compared, and emission and FC characteristics of buses were analyzed based on approximately 28,700 groups of instantaneous
data obtained in Beijing using a portable emissions measurement system (PEMS). The experimental results revealed that NOx and
PM emissions from CNG buses were decreased by 72.0% and 82.3% respectively, compared with Euro IV diesel buses. Similarly,
these emissions were reduced by 75.2% and 96.3% respectively, compared with Euro III diesel buses. In addition, CO2, CO, HC,
NOx, PM emissions and FC of Euro IV diesel buses were reduced by 26.4%, 75.2%, 73.6%, 11.4%, 79.1%, and 26.0%, respectively,
relative to Euro III diesel buses. The CO2, CO, HC, NOx, PM emissions and FC factors all decreased with bus speed increased, while
increased as bus acceleration increased. At the same time, the emission/FC rates as well as the emission/FC factors exhibited a strong
positive correlation with the vehicle specific power (VSP). They all were the lowest when VSP < 0, and then rapidly increased as VSP
increased. Furthermore, both the emission/FC rates and emission/FC factors were the highest at accelerations, higher at cruise speeds,
and the lowest at decelerations for non-idling buses. These results can provide a base reference to further estimate bus emission and FC
inventories in Beijing. 相似文献
973.
城市生活垃圾的产生量是城市环境卫生事业规划和建设的重要依据,本文运用灰色关联度方法,定量分析了影响西安市生活垃圾产生量的因素,并通过建立灰色预测模型,对西安市未来几年的生活垃圾产生量进行了预测,为西安市的城市规划提供了定量的参考依据。 相似文献
974.
目的针对BP神经网络对转子故障诊断方法存在的局限性,提出一种融合Sugeno模糊积分和BP神经网络的转子故障轴心轨迹识别诊断方法。方法首先利用轴心轨迹图像的不变矩为特征向量,提取常见旋转机械转子故障特征,随后利用多个BP神经网络对故障类型进行识别,最终采用Sugeno模糊积分对BP神经网络识别结果进行决策,从而构建转子故障诊断模型,并应用于转子系统故障的诊断。结果通过机械故障仿真模拟实验平台采集了6种常见转子系统故障信号,利用matlab2012a软件编程建模仿真处理,试验表明,该模型有效地提高了转子系统多类别故障的识别正确率。同时,该方法对同一故障类型识别所需样本少,大大节省了数据获取和处理的时间。结论该方法提出并用于转子系统故障诊断中,诊断准确性高,可靠性强,利用样本数据量少,节约时间,对小样本数据的故障诊断有着良好的效果。 相似文献
975.
Three fractions of alkaline phosphatase activity(APA), including phytoplankton APA(phyto-APA), bacterial APA(bact-APA), and free-APA, were examined in the sea surface microlayer(SML) and the subsurface water(SSW) from Daya Bay, Guishan Island, and Guanghai Bay of southern China. Relationships between APA and environmental parameters were analyzed. The growth of phytoplankton was significantly limited by dissolved inorganic phosphorus(DIP) in the three sea areas, especially in Daya Bay. TotalAPA ranged between 1.41 and 35.26 nmol/L/hr, and the highest value was found in Daya Bay. The increased APA in Daya Bay was the result of the increase of phytoplankton biomass and the response of phytoplankton to P limitation. Phyto-APA was the main contributor in Daya Bay, while phyto-and free-APA co-dominated in Guishan Island and Guanghai Bay. Bact-, phyto-, and total-APA showed a significant inverse power function relationship with DIP, and 0.2 μmol/L was the threshold for DIP on particulates and totalAPA. Pearson correlation analysis suggested that DIP limitation together with high N levels enhanced APA. High water temperature and freshwater input accelerated APA as well.Principal component analysis clearly separated samples from the three sea areas, as well as from the SML and the SSW, which indicated the differences in environmental parameters and APA levels. Our results highlight the influence of phosphorus limitation and environmental parameters on APA. 相似文献
976.
Based on the available toxicity data and the concentrations of DDTs and HCHs in surface water from the upper reaches of the Huaihe River, overlapping areas of probability density and margin of safety (MOS10) were used to estimate the risk levels of DDTs and HCHs to aquatic organisms. The overlapping areas of α-HCH, γ-HCH, p,p′-DDE, p,p′-DDD, and p,p′-DDT were found to be 9.3 × 10?5, 4.6 × 10?3, 4.3 × 10?2, 2.2 × 10?2, and 4.2 × 10?2, respectively. The risks from DDTs were higher than those from HCHs, the risk from α-HCH being the smallest. The MOS10 values of α-HCH, γ-HCH, p,p′-DDE, p,p′-DDD, and p,p′-DDT were 2.6 × 103, 97, 5.9, 15, and 8.6, respectively, i.e. greater than 1.0, indicating limited overlaps between the distributions of exposure concentrations and of toxicity data, and thus minimal ecological risk. Health risk calculations based on incremental lifetime risks for HCHs and DDTs were conducted to evaluate human cancer risk and non-carcinogenic hazard. The total cancer risks from organochlorine pesticides (OCPs) in the studied area were in the range of 10?8–10?7, lower than the baseline value of acceptable risk (10?6). Non-carcinogenic hazard indices of OCPs ranging from 10?6 to 10?5 were much lower than the threshold values (1.0). These results suggest that the water from the upper reaches of the Huaihe River does not pose any health risk for local residents using river water as a source for drinking water. 相似文献
977.
秦皇岛近岸海域环境综合整治效果及防治对策 总被引:1,自引:0,他引:1
近年来,秦皇岛市通过实施关停非法排污企业、区域限批、治理农业面源等一系列环境综合整治措施,近岸海域水质明显改善。针对秦皇岛近岸海域污染的主要原因(陆源工业废水、生活污水、畜禽养殖业废水、粪便的排放和种植业农药化肥不合理使用造成氮、磷等营养物质流失等),从调整产业结构、控制陆源污染排放和完善执法机制等方面,提出了进一步治理的综合防治对策。 相似文献
978.
Younggu Her Conrad D. Heatwole Moon S. Kang 《Journal of the American Water Resources Association》2015,51(4):1072-1087
The Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) has been a valuable resource for hydrological analysis, providing elevation data at a consistent resolution on a near‐global scale. However, its resolution (three arc‐second or 90 m) is sometimes too low to obtain the desired level of accuracy and precision for hydrologic analysis. We evaluated the performance of several methods for interpolating SRTM three arc‐second data to a 30‐m resolution grid to better represent topography and derive terrain characteristics of the landscape. STRM data were interpolated to 30‐m DEMs on a common grid using spline, inverse distance weighting (IDW), kriging (KR), natural neighbor methods, and cubic convolution (CC) resampling. Accuracy of the methods was assessed by comparing interpolated and resampled 30‐m grids with the reference data. Slope, aspect, sinks, and stream networks were derived for the 30‐m grids and compared on a cell‐by‐cell basis to evaluate their performance in reproducing the derivatives. The comparisons identify spline and KR as the most accurate interpolation methods, of which spline is preferred because of its relative simplicity. IDW provided the greatest bias in all methods with artifacts evident in slope and aspect maps. The performance of CC projection directly to a 30‐m resolution was comparable to spline interpolation, thus is recommended as the most convenient method for interpolating SRTM to a higher resolution. 相似文献
979.
980.